Ellesco
Huddersfield-based VTL Group has made significant investments in its Technical Solutions Centre, which was opened in November 2011, the latest being a UK-first installation of a PEMTec Electro-Chemical Machining system.
Developed to ensure that innovation and technology are combined to develop manufacturing processes that will help VTL deliver total quality at lower cost, the Technical Solutions Centre is a far cry from the company’s previous R&D facility; something that Mark Richardson, VTL’s Technical Development Manager, described as “a traditional toolroom”. This 22,500 ft2 facility makes use of the latest in CNC metalcutting and EDM technology to provide a first class environment to carry out the research that is vital to the future of VTL.
One of the roles of the Technical Solutions Centre is to investigate ‘alternative’ technologies and manufacturing techniques. The PEMTec Precision Electro-Chemical Machining system (PECM) from Ellesco falls squarely into this category, providing opportunities to develop new production systems by using the non-contact Electro Chemical Machining process to produce complex workpieces. The process achieves this by dissolving excess material utilising the principle of anodic solution of the workpiece in an electrically-conductive medium (electrolyte).
The PECM process is highly accurate as there is no loss of size or wear on the electrode, this also means that complex and fine detail work can be achieved, and any electrical conductive material can be ‘machined’. Further advantages of the PECM process are the fact that there is no change in the workpiece metallurgy and a high level of surface finish can be achieved (as fine as Ra 0.03 µm) with the ability to vary the surface roughness using a single tool. Additionally, as no pressure or heat is applied to the component it is possible to machine extremely thin wall thicknesses and maintain accuracy without affecting material structure.
Of particular interest to Mark Richardson and his team, though, is the potential for cycle time reduction by using PECM on certain automotive components. “Serial production is a big advantage of the process in that it takes the same time to produce ten components as it does one, assuming that they are of a size to fit on the machine table at the same time. Initially we are looking at smaller, more complex components, taking the existing conventional machining cycle time as a benchmark and investigating how PECM can improve on that.”
Time is saved by the fact that roughing, smoothing and polishing operations are carried out in the same cycle and the finished component is completely free of burrs, eliminating any secondary operations. Feedrates of between 0.1 and 2 mm per minute can be achieved depending on the material being processed, which can include more exotic materials such as Inconel and Hastalloy, with repeatable tolerances as fine as ±2 µm achievable.
The modular PEMTec system consists of four units, these being PEM-Mechanic, PEM-Control, PEM-Aqua and PEM-Power. PEM-Mechanic is the ‘machine’ part of the system and features a granite and stainless steel single-axis portal construction providing a base for the precision movement of the electrode, which vibrates at 50 Hertz and is positioned within a micron at process-related pressure pulses of over 10,000 Newton. Control is provided by the PEM-Control unit, which benefits from clearly-structured and uncomplicated operating and control software. It also makes use of multi-level, workpiece-specific, machining programmes to deliver increased flexibility. Power is delivered by PEM-Power, a modular and highly-dynamic constant supply point, which provides a high degree of power stability. From a process security point of view, the in-built PC monitors the voltage and pulse length values every 20 µ-second and if the system detects any power related problems it immediately shuts down. The final piece in the system is the PEM-Aqua module, which controls the preparation of the electrolyte in a closely monitored, environmentally friendly process that includes automatic chrome-VI reduction, conductivity pH, temperature, micro-filtering, and control of the electrolyte’s variable flow rate (between 1 – 40 l/min.).
“The installation at VTL is the first PEMTec system in the UK. We are certain, given the capabilities of the Precision Electro-Chemical process in high demand applications such as automotive, aerospace, medical implants, mould and die, and defence, it will be the first of many.
No matter how many axes, no matter how powerful the computing, or how fancy the tooling, conventional machining has its limits and now Precision Electro-Chemical Machining offers a credible alternative without those limits,” says Ellesco’s Managing Director, Vincent Simonis. “UK manufacturing industry has to look closely at the processes and technologies available to it in order to remain competitive. It is encouraging that companies, such as VTL are looking to the future to ensure that they remain competitive.”